The present invention relates generally to shift modulation controls for transmissions and more particularly to a modulation control valve for a power shift transmission.
In the past, shift modulation control valve operated in conjunction with low capacity pumps and high volume transmissions as disclosed in the U.S. Pat. No. 3,386,540 granted to J. Horsch et al. In these systems, when a sudden demand in the transmission caused the reservoir valve to open under urging of the pressurized fluid from the accumulator piston, the time lag for the pump to fill the transmission was large enough to allow the fluid pressure from the accumulator piston to be completely dissipated. With larger pumps and the desire for faster filling of the transmissions, the time lag has decreased until the accumulator piston cannot be completely relieved and thus the modulation control valve cannot operate properly.